a sail

It depends on the type of vessel and how it is rigged. The smaller sail on a standard sailing boat is the jib or genoa

Genoa is indeed a word that can be used in Scrabble. Its definition is:

a triangular sail

and is worth 6 points. You can add an 'S' to the end to make it plural.

One type is the "lateen sail", but there are also jibs; Genoa & spinnaker.

An asymmetrical spinnaker is a sail which is rigged like a spinnaker, but asymmetrically shaped like a genoa.